Adaptation and Evolution

Transcription

1 Adaptation and Evolution By Danilo Villar Rogayan Jr. Instructor I, Natural Sciences The Interaction of Ecology and Evolution Ecology study of interaction between an organism and its environment Evolution genetic change in a population of organisms over time The Interaction of Ecology and Evolution adaptation, evolutionary solution, a genetically determined characteristic that improves an organism s ability to survive and reproduce in a particular environment; evolutionary process whereby organisms become better suited to their environments The Ecological Theater and the Evolutionary Play, a book written in 1965 by renowned ecologist G.E. Hutchinson, an apt metaphor for the interaction between ecology and evolution The Interaction of Ecology and Evolution Ecology and evolution are intimately related biological fields. An organism s ecological situation determines the kinds of evolutionary forces it faces. At the same time, a species evolutionary history accounts for important aspects of its ecological relationships. Evolution in Populations Genetic Variation Some inherent variability exists among individual organisms. For any given character, different individuals exhibit different traits. 1

2 Evolution in Populations Variability has two possible bases: inherited differences and environmentally induced. phenotype, visible manifestation of a character in an organism genotype, genetic constitution of an organism In pea plants, tall pea plants (T) are dominant over short pea plants (t). Construct a Punnett Square for a heterozygous tall pea plant and a short pea plant. t t T Tt Tt t tt tt What are the percentage of phenotypes? 50% tall 50% short Fundamentals of Population Genetics Population basic evolutionary unit, a group of conspecifics inhabiting a specified geographic area Gene Pool the sum total of all the genes in a population Fundamentals of Population Genetics Populations adapt in response to selection pressures from the environment. Although natural selection is a major force in adaptation, genetic drift can also play an important role in this process. 1. Genetic Drift This represents random changes in small gene pools due to sampling errors in propagation of alleles. The bottleneck effect and founder effect are prime examples of genetic drift. In either case the number of individuals in a population is drastically reduced distorting the original allelic frequencies. 1. Genetic Drift 2

3 2. Gene Flow The movement of alleles into and out of a gene pool. Migration of an organism into different areas can cause the allelic frequencies of that population to increase. 2. Gene Flow 3. Mutations These changes in the genome of an organism are an important source of natural selection. 3. Mutations 4. Non-random Mating Inbreeding is a popular form of nonrandom mating. Individuals will mate more frequently with close individuals than more distant ones. 4. Non-random Mating 3

4 5. Natural Selection Populations vary in the types of individuals and their reproductive success. Those individuals that leave more offspring behind than others pass on more of their alleles and have a better success rate in dominating the population. 5. Natural Selection Microevolution There are 5 basic causes of microevolution: Genetic Drift: This represents random changes in small gene pools due to sampling errors in propagation of alleles. The bottleneck effect and founder effect are prime examples of genetic drift. In either case the number of individuals in a population is drastically reduced distorting the original allelic frequencies. Gene Flow: The movement of alleles into and out of a gene pool. Migration of an organism into different areas can cause the allelic frequencies of that population to increase. Most populations are not isolated, which is contrary to the Hardy-Weinberg Theorem. Mutations: These changes in the genome of an organism are an important source of natural selection. Nonrandom mating: Inbreeding is a popular form of nonrandom mating. Individuals will mate more frequently with close individuals than more distant ones. Assortive mating is another form of nonrandom mating. Here the individuals will mate with partners that closely resemble themselves in certain characteristics. Natural Selection: Populations vary in the types of individuals and their reproductive success. Those individuals that leave more offspring behind than others pass on more of their alleles and have a better success rate in dominating the population. Macroevolution Speciation and the origin of the divisions of the taxonomic hierarchy above the species level, and the development of complex organs Cannot be witnessed because it occurs over intervals that far exceed the human lifespan 1. Stasis Many lineages on the tree of life exhibit stasis, which just means that they don't change much for a long time. A coelacanth swimming near Sulawesi, Indonesia 4

5 2. Character Change Lineages can change quickly or slowly. Character change can happen in a single direction, such as evolving additional segments, or it can reverse itself by gaining and then losing segments. Changes can occur within a single lineage or across several lineages. 2. Character Change 4. Extinction Extinction is extremely important in the history of life. It can be a frequent or rare event within a lineage, or it can occur simultaneously across many lineages (mass extinction). 4. Extinction 3. Lineage-splitting (or Speciation) Patterns of lineage-splitting can be identified by constructing and examining a phylogeny. A phylogeny represents evolutionary relationships among organisms and represent them on a family tree known as phylogenetic tree. 3. Lineage-splitting (or Speciation) 5

6 1. Allopatric Speciation 2. Sympatric Speciation 3. Phyletic Speciation Speciation is a lineage-splitting event that produces two or more separate species. 1. Allopatric Speciation extrinsic factors (geographic barriers) prevent two or more groups from mating with each other regularly, eventually causing that lineage to speciate If the separation between groups continues for a long period of time, the differences between their alleles can become more and more pronounced due to differences in climate, predation, food sources, and other factors, eventually leading to the formation of a new species 1. Allopatric Speciation 2. Sympatric Speciation occurs when two individual populations diverge from an ancestral species without being separated geographically the process through which new species evolve from a single ancestral species while inhabiting the same geographic region exploiting a new niche may automatically reduce gene flow with individuals exploiting the other niche. 2. Sympatric Speciation 3. Phyletic Speciation Suggests that abrupt mutations in a few regulatory genes occur after a species has existed for a long period of time. This mutation results in the entire species shifting to a new species. Apple maggot pies apples hawthornes 6

7 3. Phyletic Speciation Summary Patterns and Processes in Biogeography Microevolution Macroevolution Mechanisms 1. Genetic Drift 2. Gene Flow 3. Mutations 4. Non-Random Mating 5. Natural Selection Patterns 1. Stasis 2. Character Change 3. Extinction 4. Lineage Splitting or Speciation (Allopatric, Sympatric, Phyletic) Mimicry the physical resemblance of two or more species resulting from inherent advantages of similar appearance. Coevolution interactions in which each species has exerted a crucial selective force on the other; interdependent evolution of two or more species that have an obvious ecological interaction. Association Effects Species A Species B Parasitism + - Commensalism + o Mutualism + + Predation/ + - Herbivory Competition - - Figure 1. The Effects of Various Kinds of Interactions 1. Parasitism an interaction in which individuals of one species the parasite derive their nutrition from the living tissues of a host species; the parasite benefits from the interaction, but its host s fitness is lowered. ex. beef tapeworm (Taenia saginata) in humans; sheep liver fluke (Fasciola hepatica) commensalism, an interaction in which one species benefits but the other is neither helped nor harmed ex. myxomatosis virus and European hares (Oryctolagus cuniculus) 7

8 1. Parasitism an interaction in which individuals of one species the parasite derive their nutrition from the living tissues of a host species; the parasite benefits from the interaction, but its host s fitness is lowered. Wasp eggs on back of caterpillar. ex. beef tapeworm (Taenia saginata) in humans; sheep liver fluke (Fasciola hepatica) commensalism, an interaction in which one species benefits but the other is neither helped nor harmed ex. myxomatosis virus and European hares (Oryctolagus cuniculus) Mosquito biting a human. Parasitism Sea lampreys feed on fluids of other fish. 2. Mutualism an interaction in which both individuals benefit from the interaction ex. hermit crabs and sea anemones; tanagers and mistletoes; yucca (Yucca spp.) and yucca moth (Tegeticula yuccasela) 3. Competition an interaction between two species over a limiting resource that negatively affects their population growth rates. 8

9 Monkeys compete with each other and other animals for food. 4. Predator-Prey and Herbivore-Plant Evolution among the most complex evolutionary and ecological systems predation, the capture, killing and consumption of an animal, usually by another animal herbivory, the consumption of plant tissue by an animal Rams compete with each other for mates. ex. frog-eating bat (Trachops cirrhosus) milkweed (Asclepias spp.) and larvae of the monarch butterfly (Danaus plexipus) References: Krohne, David T General Ecology, 2 nd Edition. Cengage Learning Asia Pte Ltd: Singapore. Fernandez, Elsha Vienna M Biological Science: A Reviewer for the Licensure Examination for Teachers. PNU University Press : Taft Avenue, Manila. Melchor, Marciano B., et al Laboratory Manual in Biology. Rex Book Store: Manila, Philippines. Lakô hã salamát! Maraming salamat! 9